Current automotive vehicles and trucks include a multi-speed power transmission. The use of planetary gearsets and automatic shifting power transmissions has become more prominent in the field of vehicle transportation. The planetary transmissions employed in the powertrains generally include two or more planetary gearsets and a plurality of fluid-operated torque-transmitting mechanisms, commonly termed clutches and brakes.
While these arrangements operate very well and provide for simplicity of operation, it is desirable to improve efficiency of these units. One way of improving the efficiency is to remove the hydraulic components from the transmission. This, of course, was done in many previous power transmissions utilizing countershaft arrangements and synchronizer shifting mechanisms. The synchronizer shifting mechanisms generally employed a manual control mechanism, thereby eliminating the need for high pressure hydraulic fluid within the transmission control system.
More recently, it has been found that the planetary-type gearset will lend itself quite well to mechanical- or synchronizer-type clutches and brakes.